The invention relates to a pressing tool for jointing clamps of various sizes.
Pressing tools for pressing casing-like press fittings home on pipe ends must guarantee that the jointing clamps always press the press fitting home properly. For the common press fitting diameters, appropriate jointing clamps are insertable in any given case into the pressing tool. Because great forces are required for pressing home, a hydraulic cylinder is used for actuating the jointing clamps in various known pressing tools. Embodiments are known from U.S. Pat. No. 5,125,324 where an electric motor drives a hydraulic cylinder. The fluid acted upon by pressure is guided into a hollow cylinder to activate a piston which activates the pressing tool or the jointing clamp. A compact activation unit arises through the pump with electric motor arranged directly on the lifting cylinder. At the end of the pressing process, excessive pressure arises in the cylinder, which leads to opening the excess pressure valve and therewith to ending the pressing process. The piston is reset by a return spring while recirculating the liquid into a collection area. Monitoring complete pressing home takes place through the threshold pressure which is necessary for opening the excess pressure valve. Different forces of pressure are needed for optimal pressing home of various press fittings in any given case. With a pressing tool which generates a force which goes beyond the necessary pressing force due to a fixed threshold pressure for all pressing processes between the open dies, a large proportion of the force is absorbed by the open dies. These must correspondingly be constructed with excessive dimensions and are subject to increased abrasion. If the open dies jam, then the threshold pressure, and consequently the end of the pressing process, can be reached without the press fitting being pressed home correctly.
From DE 297 14 753 U1, a pressing tool with two interacting open dies is known where a spacing receiver is constructed between the open dies. Here a relocatably mounted plastic stop pin pressed from the outside by a spring from the first open die projects against a stop face of the second open die. If the open dies are moved toward one another, the pin is pressed into the first open die by the stop face. A metal casing fixed upon the pin is moved over the area of two sensors when the bolt is moved. The oscillating circuits of the sensors are detuned on the basis of an eddy current induction when a metal casing is placed significantly close. Three different fastening bolt position ranges can be recorded. In a first position range, the casing is only in the vicinity of the first sensor. In a second position range, casing segments are in the vicinity of both sensors. In a third position range, the casing is only in the proximity of the second sensor. The casing and the sensors are now dimensioned or set at a distance such that the first position range is allocated to bringing the open dies together before the pressing process. The second position range is allocated to the pressing process and reaching the third position range corresponds to the end of the pressing process.
This spacing receiver can consequently be used for ending the pressing process. Here, entering into a specified position range is recorded for ending the pressing process between the open dies. All usable jointing clamps must consequently have a spacing receiver. After inserting a jointing clamp, the spacing receiver must be connected with the control unit of the pressing tool. The advantage of a jointing clamp position recording is associated with the disadvantage of the expensive construction of the jointing clamp and the expense of a separate electrical connection of the jointing clamp to the pressing tool.
A crimping tool for pressing home electrical cables with connections is known from U.S. Pat. No. 5,113,679 which supplies the activation pressure when two grips are pressed together with a pump cylinder. During extrusion, a tamping tool connected to the press plunger is moved against a crimp anvil by the press plunger In order to be able to measure the position of the stamping tool, an electrical resistor strip is provided on the crimping tool and contact elements which can be slid over it are provided on the press cylinder. Owing to contamination or oxidation of the resistor strips, false positional values can be recorded. With false positional values, even the quality of the pressure can be falsely indicated, which impairs an efficient operation with the crimping tool. Moreover, no casings can be pressed home.
Underlying the invention is the objective of finding a safely operating pressing tool. In addition, a pressing process with such a pressing tool should guarantee that the pressing can be safely implemented with all insertable jointing clamps.
In accomplishing the objective, it was recognized that with a contact-free or contactless measuring position measuring device which makes the piston position continuously recordable over a positioning range. The current piston position can be determined with certainty at least at one point in time. It thus does not need to be fixed in advance at which position a jointing clamp present check should be conducted by the positioning of a presence sensor. Any desired piston position can be recorded within the positioning range. Because the position recording takes place contact-free or without contacts, no disturbances can occur owing to contaminated sliding contacts. The at least one point in time in which the position should be measured depends upon the activation process. In extruding a press fitting, the piston position is preferably recorded when the threshold pressure is reached, directly before a return valve is opened, or forwarded to a control unit or comparison unit. This piston position is a measure for the quality of the extrusion because the maximal feed obtained is associated with most narrow open die position derivable from the open die shape or mounting or by the open die parameters. If the threshold pressure is reached before complete extrusion, then in this way a piston position is detected which does not correspond to a specified piston position range value, or which does not lie in a tolerance range around the piston position range value. On the basis of the comparison of the piston position recorded with at least one lower range threshold, the quality of the extrusion can be characterized.
With the preferred embodiment of the pressing tool, the result of the comparison is used to initiate a two-valued indication. With a complete extrusion, for example, a green signal is turned on and/or with an incomplete extrusion, for example, a red signal is turned on. It is obvious that, instead of an indication, a signal tone can also be provided. If attaining an effective open die position is being examined, errors which arise in connection with a pressure monitoring can be ruled out. The jointing clamps require no spacing receiver. Any number of standard jointing clamps can be used. The pressing process can be conducted independently of position monitoring whereby, however, position recording serves to monitor the quality of extrusion.
If need be, however, the position measuring device is connected with the control unit of the pressing tool. Then the drive of the fluid pump and/or at least one valve of the fluid conduit system can be controlled independently of a recorded piston position. Preferably, the pressing process is ended upon reaching a piston position necessary for complete extrusion. In this way, building up a standard threshold pressure can be dispensed with. In addition to process control on the basis of continuous monitoring to the piston position, and in particular current open die parameters, a magnitude derived from piston positions, such as piston speed or piston acceleration, can be used to influence the course of the process.
The pressing tools in accordance with the state of the art can be used with many different interchangeable jointing clamps. The various jointing clamps are constructed for pressing copper and steel fittings with diameters of 12, 15, 18, 22, 28, 35, and 54 mm, or for joining plastic pipes with diameters of 16, 20, 25, 32 mm. In addition to these standard magnitudes, special jointing clamps are also known for connections with diameters of 76.1, 88.9 and 108 mm. It is evident that the insertable jointing clamps can have any desired pressing diameter. In accordance with the respective guide of the open die motion and the connection to the piston rod, a coordination between the desired position of the open die in connection with complete extrusion and the piston position necessary for this for all jointing clamps is to be determined.
If the piston position required for the various jointing clamp sizes is different, then preferably a recording unit is provided which makes a jointing clamp coordination, preferably a piston end position or a range for it, inputtable or recordable. In this way, it should be guaranteed that the comparison of the recorded piston position always takes place with the correct position range value for the jointing clamps used. For this, the measuring unit is connected with the control or comparison unit.
If the operators must input the identification for the current jointing clamp on the recording unit, then a monitoring device can be provided which requires inputting the identification of the new jointing clamp when changing a jointing clamp or when inserting the fastening bolt. The recording unit is, however, preferably equipped with a sensor device and can therewith automatically identify or record the jointing clamp inserted, especially the piston end position allocated to it. The identification should take place free of contacts or without contacts because otherwise disturbances can occur due to contamination, oxidation or short circuit. A preferred solution provides that the sensor device includes at least one Hall sensor allocated to the pressing tool which identifies the jointing clamp or the corresponding piston end position on the basis of the magnetic field originating jointing clamp. Disturbances of jointing clamp coordination as a function of contamination or moisture can be ruled out by measuring of a magnetic field characteristic. In order to make 32 different jointing clamp coordinations possible with little expenditure, the possibility of installing a permanent magnet or coordination magnet is provided at about five positions on the jointing clamp. For this, blind bore holes are created. The positions for coordination magnets lie opposite appropriately arranged coordination Hall sensors when the jointing clamp is inserted so that the coordination Hall sensors make the presence of coordination magnets possible. A greater number of coordinations is made possible through a larger number of Hall sensors and positions for magnets.
If a jointing clamp characterization is used as a coordination, then the pressing tool must assign a piston position range value to each jointing clamp characterization in order to be able to compare the current piston position with this range value characterizing a complete extrusion at the end of the pressing process. With such a two-stage coordination, the problem emerges, however, that the tables of the pressing tool are supposed to be supplemented in connection with the appearance of new jointing clamp types. It has become apparent that the most efficient coordination possible does not emerge from recognizing the type of the jointing clamp, but rather directly from the recognition or coordination of the piston or the piston position range value. If thus the coordination classes described as above by means of five magnet positions 25, or 32, then 32 different piston position range values can be defined in the pressing tools. The jointing clamps to be recognized must then in any given case be attributed to one of these 32 classes. This assignment is possible for new types of jointing clamps and even for jointing clamps from other manufacturers as long as the piston end position required lies in a predefined range. Then it only needs to be guaranteed for the proper range value allocation that the jointing clamp is provided with magnets at the right places. It would also be possible, if need be, for the user of such pressing tools to be able to construct a coordination himself by applying blind bore holes and pressing in the magnets.
With a coordination of the piston position range value of this type, it is possible for jointing clamps of wholly different sizes to be characterized identically because the piston end position for these jointing clamps lies in the same range. Because the overall range in which the piston position range values of current jointing clamps only extends over ca. 20 mm, a coordination with 32 part ranges suffices. With a less fine distribution, fewer than five positions for magnets would suffice. With a larger overall range and/or more narrow part ranges, more than five positions could also be provided for coordination magnets. At the end of each pressing process, the current piston end position is compared with the piston end range value allocated to the jointing clamp. If the current position end value of the piston lies under the piston position range value or beneath the allocated tolerance range, then the jointing clamp was not completely closed, which is indicated preferably by a warning signal. If the current position end value lies above the piston position value range or above the allocated tolerance range, the jointing clamp is deformed or broken which once again is preferably indicated by means of a warning signal. This can also, if need be, lead to switching the pressing tool off.
The lifting cylinder device of the pressing tool is an activation module which makes great forces available in the piston feed direction, and makes any desired piston positions exactly measurable over the entire positioning range on the basis of the position measuring device. Because the cylinder element is arranged connecting directly to the fluid pump with drive, a compact construction results. The fluid conduits and at least one valve are arranged in the joining area of the pump and the cylinder element. The drive is preferably connected through a power transmission with the pump and can be adapted to the use in question. The drive motor of the pump is preferably an electric pump whose actuation is connected with the control unit of the lifting cylinder device. This control unit makes the triggering of a desired activation sequence through an actuation connection. A resetting element, especially a return spring, is arranged preferably in the cylinder element for resetting the piston. The piston rod is guided from the cylinder element as an activation part.
In order to use the cylinder space as optimally as possible with a hydraulically activated piston, a fluid receiving area is constructed on the side of the cylinder facing away from the activation pressure, thus in the region with the return spring. For this, the cylinder element is tightly closed off on both front faces. The piston rod is correspondingly passed through a seal.
The position measuring device which measures free of contacts or without contacts makes possible, preferably, a distance measurement between the cylinder element and the piston, whereby preferably a Hall sensor and a magnet or a position Hall sensor and a position magnet, if necessary a laser interference or laser diffusion distance sensor and a reflection surface are arranged or constructed on each one of the two elements. When using a Hall sensor, this is preferably fastened on the cylinder element in the region of the front face, especially on the front face with pressure fluid feed. The magnet or position magnet is arranged on the piston. The magnetic field strength in connection with the Hall sensor or position Hall sensor, which measures this, depends upon the piston position or on the position of the magnets. A piston position can now be allocated to each value of the Hall sensor by means of a calibrating curve. Care must be taken in connection with the placement of the Hall sensor and the magnets that an unambiguous coordination between the measured value of the Hall sensor and the piston position is guaranteed in the entire desired position range. The distance measurement with the Hall sensor can be conducted sufficiently accurately with economical and small components.
With laser interference measurement and laser diffusion measurement, the laser light reaches from one front face of the cylinder element over a reflection on the piston back to the front face again. The piston position is determined from the phase shift between the outgoing beam and the beam reflected on the piston with interference measurement. With laser diffusion measurement, the intensity of the light reflected on the piston is used as a measure for the piston position. In addition to distance measurements with light, analogous measurement devices with high frequency ultrasound are possible, whereby then, however, problems can arise due to pressure oscillations in the pressure fluid because the speed of sound propagation depends upon pressure. Moreover, the laser and ultrasound systems are still relatively expensive at this time, so that measurement with a Hall sensor is preferable.
In addition to effective distance measurement, the position measurement device with position readings, especially with an increment scanner, is very widespread and correspondingly beneficial. For this, a reading head must be movable along a scale. When measuring the piston position in the cylinder element, the reading head is fastened preferably on the cylinder element owing to the connecting cable. Correspondingly, the scale is fastened on the piston or on the piston rod, or is set in motion by this by a transmission of motion. Since the piston rod is guided through a seal in a preferred, compact construction of the lifting cylinder device, the scale must also be passed through this seal. The reading head is then arranged on one of the two sides of the seal. The scanning takes place optically or inductively. Since inductive scanning is possible without problems on a band with locally different magnetization, an inductive scanning is consequently preferred. Such magnetized measurement bands are robust and can perhaps be pressed into fitting depressions in the piston rod so that the piston rod can be sealed off.
A further aspect is that, in order to increase safety for operators as well as for the pressing tool, and to increase the quality of extrusion, a jointing clamp presence check is helpful. The pressing process is not conducted flawlessly when the jointing clamp is improperly inserted, and the forces arising can damage the pressing tool. Operating personnel can also be injured in this context. This jointing clamp presence monitor can be installed in pressing tools independently of the piston position measuring device.
The jointing clamp presence check prevents initiating a pressing process as long as no jointing clamp is inserted into the fork-shaped connection element. If no jointing clamp inserted in an orderly manner is available after a specified delay period and repeated jointing clamp monitoring, the pressing tool is returned to the initial state. Once the pressing process has been initiated, then the jointing clamp presence check leads to an interruption of the pressing process if the joint tool no longer sits correctly in its anchoring. With this jointing clamp presence monitoring, the same applies as with jointing clamp coordination. It should be a check which functions even with strong contamination and in a moist environment. Therefore a sensor which measures without contact, which makes a field property determinable, which is clearly distinguishable when the jointing clamp is present and absent [is required]. For this, for example, a presence magnet can be provided on the jointing clamp which is recordable by a presence Hall sensor of the pressing tool. Because even old jointing clamps or jointing clamps by other manufactures should be installable, it is, however, advantageous to install an inductive sensor for jointing clamp presence monitoring which makes the presence of any desired jointing clamp detectable. But other sensors or mechanical switches can also be installed which respond upon contact.
If the jointing clamp is present, it must in addition be assured that the fastening bolt which connects the jointing clamp with the pressing tool is properly installed. Since it was established that a pure bolt latching check guarantees no sufficient security against a partial insertion, or in the worst case with the fastening bolt sliding out, a bolt latching check is described with which a completely installed fastening bolt can be moved or rotated into a latching position which is monitorable. A sensor which measures without contact should be used which makes a field characteristic determinable which is clearly distinguishable in connection with the presence or absence of securing the fastening bolt. For this, a latching element of the fastening blot nay be provided with a latching magnet which in the latched state or in the latching position bounds upon a latching sensor in the pressing tool. If the latching sensor detects a magnet, then the fastening bolt is in the latching position. It is obvious that instead of the Hall sensor, for example an inductive sensor can also be used. Since the fastening bolt belongs to the pressing tool, one may proceed from the assumption that the pressing tool is always outfitted with a fastening bolt with latching magnets.
In order to be able to check with little expenditure whether the jointing clamp is properly or securely installed, the presence sensor and the latching sensor are arranged in a series or circuit. The pressing tool is preferably only activatable if the jointing clamp is installed and the fastening bolt is latched. If need be, however, the presence of the jointing clamp is provided for the activatability of the pressing tool, and fastening bolt which is not latched leads to an acoustic and/or optical warning signal. If, despite the warning signal, a pressing process is triggered, then the unbraked piston motion can lead to damage to the pressing tool. In order to retain the reason for such damage for guarantee or product liability questions, it is appropriate to store the activation without secured fastening bolt in a fault storage.
Since the possibility of insertion of a jointing clamp without fastening bolts is more difficult than installing a fastening bolt without jointing clamp, the jointing clamp presence check is more secure with relation to the jointing clamp as a condition for the ability to implement a pressing process than checking whether a fastening bolt is inserted or latched.
A pressing tool with a latching sensor which measures without contact, preferably with a Hall sensor, is also new and inventive independently of a position measuring device. The detection of the latching or a securing measure has the advantage in relation to the state of the art in accordance with European patent application No. 95810595.9-2306 that an undesired motion or falling out of the fastening bolt can be ruled out. Further advantageous embodiments arise in combination with a presence sensor which have already been described above on the basis of the pressing tool with the position measuring device. Here it should be considered that, in addition to the presence of the latching sensor and if need be the presence sensor, their usexe2x80x94as will be discussed by way of example belowxe2x80x94is also new and inventive in the pressing process, especially independently of the use of the piston position detection and/or jointing clamp coordination.
With the sensors described above for the jointing clamp presence check, the bolt latching monitoring and the coordination detection, a pressing process can be conducted in connection with which the extrusion is securely implementable with all installable jointing clamps. The pressing process includes initializing steps or tests after turning on the pressing tool. Before a pressing process is rendered capable of being triggered, a jointing clamp presence check takes place which detects whether a jointing clamp is installed or not. If no jointing clamp is present, an acoustic and/or optical indication signal is triggered and subsequently the jointing clamp presence check is conducted again. If still no jointing clamp is installed, or is defectively installed following a delay period, the pressing tool is returned to the initial state by a delay period facility. The pressing tool cannot be started. In order to initiate a pressing process again, a jointing clamp must be introduced into the pressing tool and fastened to the pressing tool by means of the fastening bolt. In the event that a jointing clamp was already present, care must be taken that the jointing clamp in correctly inserted into the connection element. If it is detected in the jointing clamp presence check that a jointing clamp is installed, then a coordination detection is conducted after a short delay time. Here a standard range or standard values are allocated in connection with defective coordination. As a further check prior to approval of the triggerability of a pressing process, a bolt latching check is conducted. For conducting the latching check, the pressing tool includes at least one sensor, especially one which measures without contact. If the fastening bolt is not latched, or in the securing position, this is detected by the latching sensor and indicated at least with an acoustic and/or optical warning signal. If need be, the bolt latching check is repeated until the fastening bolt is latched or secured. Following successful implementation of these surveillance steps, the pressing tool is ready for triggering a pressing process.
The pressing process is associated with further monitoring checks. For this, reaching a pressure valuexe2x80x94in particular, the time elapsed until a pressure value is reachedxe2x80x94is monitored in the lifting cylinder device. When this pressure value is reached, the current piston position is detected and a resetting procedure is conducted to reset the piston. A time control determines whether the time required to attain the pressure value lies above a specified threshold time. If this is the case, then an acoustic and/or optical warning signal is triggered and preferably an appropriate error code is stored. If the piston end position detected does not correspond to the piston position range value corresponding to the coordination detected or does not lie within the appropriate tolerance range, then an acoustic and/or optical warning signal is triggered and preferably an appropriate error code is stored.
Before a further pressing process is made triggerable, the sequence described above with a jointing clamp presence check, a coordination check and a bolt latching monitoring takes place again. In order to prevent the possibility of a jointing clamp being removed after these control operations and a pressing process being subsequently triggered, the monitoring steps are repeated at specified intervals of time or, if need be, in connection with the triggering activation for a pressing process. If during a specified maximal resting time no pressing process is triggered, then the pressing tool is shut off.